Itchy papules on an ­infant's torso and palms

A previously healthy 9-month-old infant was seen for a rash of three weeks duration. The infant had become increasingly irritable and was feeding poorly. She remained afebrile and had no other associated symptoms. A presumptive diagnosis of impetigo was made, but the eruption failed to respond to topical mupirocin (Bactroban, Centany).

Further questioning revealed that both parents began itching about a ...